Design and build (8)
I believe the answer is:
engineer
'design and build' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for engineer that I've seen before include "One uses scientific knowledge to solve practical problems" , "Mechanic" , "Person in charge of building bridges, etc." , "Practical technologist" , "One uses science to solve practical problems" .)